'Super-Jupiter' Discovery Dwarfs Solar System's Largest Planet

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In a rare direct photo of a world beyond Earth, astronomers have
spotted a planet 13 times more massive than Jupiter, the largest
planet in our own solar system.

The planet orbits a star called Kappa Andromedae that is 2.5
times the mass of the sun and is located 170 light-years away
from Earth. As a gas giant larger than
Jupiter, it's classified as a "super-Jupiter."

Astronomers say the object's immense size places it right on the
edge of the classifications for giant planets and a type of
failed star known as a brown dwarf. Its official name
is Kappa Andromedae b, or Kappa And b for short, and it
likely has a reddish glow, researchers said.

"According to conventional models of planetary formation, Kappa
And b falls just shy of being able to generate energy by fusion,
at which point it would be considered a brown dwarf rather than a
planet," Michael McElwain, a member of the discovery team at
NASA's Goddard Space Flight Center in Greenbelt, Md., said in a
Nov. 19 statement. "But this isn't definitive, and other
considerations could nudge the object across the line into brown
dwarf territory." [ Super-Jupiter
Discovery in Photos (Gallery) ]

The object is an interesting test case for theories of planet
formation, scientists say. Based on observations of this system,
the super Jupiter appears to have formed in the same way
ordinary, lower-mass exoplanets do, by coalescing from a
"protoplanetary disk" of material orbiting a nascent star.

That's because its orbit, somewhat wider than the path Neptune
takes around our sun, is at a comparable distance to planetary
orbits in the solar system. Additionally, its star, Kappa
Andromedae, is relatively young, at about 30 million years old
(for comparison, the sun is roughly 5 billion years old). These
clues point toward a formation story typical of smaller planets.

Previously, some scientists had doubted that such large stars
could give birth to planets in protoplanetary disks. The new
finding indicates that this star probably did just that.

The new photo was snapped by Japan's Subaru 8-meter telescope on
the summit of Mauna Kea in Hawaii. Alien
planets are extremely difficult to
image directly because their stars are always so much
brighter, and outshine any planets.

To capture this picture, astronomers looked in infrared light,
and used a technique to hide the glare from the star in order to
reveal the relatively faint dot of light from the planet. More
than 800 planets have been discovered beyond the solar system,
but only a handful have been imaged directly so far.

The parent star of Kappa And b, Kappa Andromedae, can be seen by
stargazers from Earth without requiring a telescope, NASA
officials said. The star can be easily seen in the night sky
above the constellation of Pegasus from suburban areas, they
added.

The discovery will be published in an upcoming issue of the
Astrophysical Journal Letters.

This story was updated at 4:26 p.m. ET to include new comments on
the Super-Jupiter discovery.